A chemical element is defined solely by the number of protons in its nucleus, known as the atomic number. Historically, elements up to uranium (atomic number 92) were discovered by isolating them from naturally occurring minerals and compounds. Modern science has reached the limit of what nature provides, meaning that all subsequent discoveries are acts of creation. Today, the search for new elements takes place inside sophisticated laboratories where scientists fuse atomic nuclei together to extend the periodic table.
Methods for Finding Elements
The journey of discovery is sharply divided by the source of the element. For elements with atomic numbers up to 92, the method was one of separation and identification, often involving chemical processes to break down complex substances found in nature.
The discovery method fundamentally changed after element 92. All subsequent elements are known as transuranic elements. These elements are inherently unstable and decay quickly, meaning they no longer exist on Earth. Therefore, the only way to confirm their existence is by actively synthesizing them in a laboratory setting. This modern approach shifts the focus to high-energy nuclear physics.
Synthesizing New Nuclei
The creation of new elements relies on powerful machines called particle accelerators, such as cyclotrons or synchrotrons, which are designed to initiate nuclear reactions. The technique involves a process of nuclear fusion where scientists accelerate a beam of lighter nuclei, known as the projectile, toward a target composed of very heavy nuclei. For instance, an experiment might use a beam of calcium-48 (20 protons) fired at a californium-249 target (98 protons) to attempt the creation of an element with 118 protons.
The projectile nuclei are accelerated to about one-tenth the speed of light, providing the necessary energy to overcome the enormous electrostatic repulsion between the positively charged nuclei. The collision energy must be precise; too low, and the nuclei simply repel, but too high, and they shatter. When the collision is successful, the two nuclei briefly fuse into a highly energized, single compound nucleus. This compound nucleus must then “cool down” by expelling a few neutrons, a process called fusion-evaporation, before stabilizing for an instant as the new, heavier element. The success rate for this fusion is extremely low, with only a few atoms of the new element created after weeks or months of continuous bombardment.
Observing the Evidence of Creation
Confirming the creation of a new, superheavy element is challenging because these atoms are incredibly unstable, often existing for mere milliseconds before decaying. Since the atom’s existence is so fleeting, scientists cannot perform traditional chemical analysis to verify its identity. Instead, researchers rely on a distinct signature: the radioactive decay chain. The newly formed nucleus immediately begins a series of alpha decays, where it sheds alpha particles, which are essentially helium nuclei consisting of two protons and two neutrons.
Each alpha decay transforms the parent nucleus into a specific, slightly lighter daughter nucleus. The scientists track the characteristic energy and time interval of each decay event in this chain using specialized detectors. The sequence of daughter isotopes must perfectly match the specific, predicted chain calculated by nuclear theory. This unique sequence of breakdown products, ending in a known, lighter isotope, provides the definitive physical evidence that a new element was momentarily created before it began its rapid disintegration.
The Official Process of Validation
Once a research laboratory believes it has successfully synthesized a new element, the discovery claim must be formally verified by the international scientific community. This responsibility falls to a Joint Working Party (JWP) composed of experts from the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP). The JWP meticulously examines the evidence, including the decay chain data and the experimental setup, to ensure the results are robust and unambiguous.
A claim is only recognized as valid if the original experiment can be successfully reproduced by other independent laboratories. This requirement for independent corroboration ensures that the discovery is a genuine scientific finding and not a statistical fluke. If the JWP validates the claim, the official discoverers are granted the honor of proposing a permanent name and chemical symbol for the new element. This final step formalizes the element’s place on the periodic table for all time.